We propose to develop a non-invasive device to enable children with urea cycle disorders (and their parents, guardians, and physicians) to actively manage the disorder at home and improve outcomes in the clinic. Urea cycle disorders (UCD) are inborn errors of metabolism that impair one's ability to convert ammonia (NH3), a neurotoxin, into urea, which is renally cleared from the body. An accumulation of ammonia in the body, known as hyperammonemia (HA), initially presents with non-specific behavioral symptoms (e.g., lethargy, hyperactivity), and if not treated can result in seizure, coma, permanent brain damage, and death. Currently, if HA is suspected in a UCD patient, the patient is taken to an emergency department and ammonia concentration is measured in the blood, which is notoriously inaccurate due to the continued production of NH3 in blood samples prior to analysis. This often erroneous measure of blood ammonia dictates the clinical course of treatment for HA, which ranges from administering intravenous fluids, nitrogen scavenging drugs, or in severe cases, dialysis. Children with UCD (and their parents or guardians) currently have no means to manage UCDs at home, and tools available in the clinic are inaccurate and slow, which can result in inadequate or mistreatment of HA. Thus, a significant opportunity exists to improve the health and care of children with UCDs by providing a more effective instrument to monitor NH3 in the body. Our vision is to provide UCD patients and clinicians who care for UCD patients with an accurate, portable, and non-invasive device to monitor a patient's ammonia level by measuring breath-borne ammonia using laser absorption spectroscopy. The envisaged product intends to provide a new means to detect the onset of HA for children at home, enabling treatment to be administered at home before ammonia accumulates to dangerous levels. The product will also enable rapid, real-time, and non-invasive measurement of ammonia, enabling physicians to administer optimal, rate-based treatment of HA in the clinic. In this Phase I Small Business Technology Transfer grant, Lumina Diagnostics proposes to establish the commercial feasibility of such a product by: (1) demonstrating and evaluating two different spectroscopic strategies for measuring gas-phase ammonia to optimize the proposed device in terms of cost and reliability; (2) demonstrating a novel breath sampling technique to increase signal levels and simplify breath collection procedures for children; (3) conducting a pilot clinical study using the proposed sensor to measure the relationship between blood-ammonia and breath- borne ammonia in UCD patients and cases of hyperammonemia. Accomplishment of these objectives will remove the main technological and clinical risks related to the proposed product. Successful commercialization of the product by Lumina Diagnostics will allow children with UCD (and their parents and guardians) to restore some normalcy to their lives by being able to actively manage their disease.